sccp.h

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#pragma once
 
#include "mim/phase.h"
 
namespace mim {
 
/// SCCP - Sparse Conditional Constant Propagation - but propagates **arbitrary expressions**.
/// @see [Constant propagation with conditional branches](https://dl.acm.org/doi/pdf/10.1145/103135.103136)
///
/// Lattice per Lam::var:
/// ```
///  ⊤      ← Keep as is
///  |
/// Expr    ← Whole expression is propagated (vertically) through var
///  |
///  ⊥
/// ```
/// @pre EtaConv ran beforehand, so no rewritable Lam escapes as a value.
/// Otherwise, the vars of such unknown functions would have to be pinned to ⊤.
class SCCP : public RWPhase {
private:
    class Analysis : public mim::Analysis {
    public:
        Analysis(World& world)
            : mim::Analysis(world, "SCCP::Analyzer") {}
 
    private:
        const Def* propagate(Lam* lam, const Def* var, const Def* def);
        const Def* rewrite_imm_App(const App* app) final;
    };
 
public:
    SCCP(World& world, flags_t annex)
        : RWPhase(world, annex, &analysis_)
        , analysis_(world) {}
 
private:
    const Def* rewrite_imm_App(const App* old_app) final;
 
    Analysis analysis_;
    Lam2Lam lam2lam_;
};
 
} // namespace mim